From 8ca86d3d353f7b14def37f7458deff28f90b6055 Mon Sep 17 00:00:00 2001
From: Simon Forman <sforman@hushmail.com>
Date: Fri, 3 May 2019 15:21:29 -0700
Subject: [PATCH] A Tracing Meta-Interpreter for Thun

---
 thun/metalogical.pl | 55 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)
 create mode 100644 thun/metalogical.pl

diff --git a/thun/metalogical.pl b/thun/metalogical.pl
new file mode 100644
index 0000000..440d13c
--- /dev/null
+++ b/thun/metalogical.pl
@@ -0,0 +1,55 @@
+% A Tracing Meta-Interpreter for Thun
+
+alpha(true).
+alpha((A, B)) :- alpha(A), alpha(B).
+alpha(number(A)) :- !, number(A).
+alpha(var(A)) :- !, var(A).
+alpha(!) :- !.
+
+% Meta-logical print trace.
+% (Could also be captured in a list or something instead.)
+alpha(thun(E, Si, _)) :- portray_clause(Si-E), fail.
+
+alpha(Goal) :-
+    checky(Goal),
+    clause(Goal, Body),  % doesn't work for e.g. +
+    alpha(Body).
+
+checky(Goal) :-
+    Goal \= true,
+    Goal \= (_,_),
+    Goal \= var(_),
+    Goal \= number(_),
+    Goal \= !.
+
+/*
+
+[debug]  ?- alpha(thun([1, 2, swap], Si, So)).
+_-[1, 2, swap].
+[1|_]-[2, swap].
+[2, 1|_]-[swap].
+[1, 2|_]-[].
+So = [1, 2|Si] ;
+false.
+
+[debug]  ?- alpha(thun([[1], 2, swons], Si, So)).
+_-[[1], 2, swons].
+[[1]|_]-[2, swons].
+[2, [1]|_]-[swons].
+[2, [1]|_]-[swap, cons].
+[[1], 2|_]-[cons].
+[[2, 1]|_]-[].
+So = [[2, 1]|Si] .
+
+[debug]  ?- alpha(thun([[1], 2, [swons], i], Si, So)).
+_-[[1], 2, [swons], i].
+[[1]|_]-[2, [swons], i].
+[2, [1]|_]-[[swons], i].
+[[swons], 2, [1]|_]-[i].
+[2, [1]|_]-[swons].
+[2, [1]|_]-[swap, cons].
+[[1], 2|_]-[cons].
+[[2, 1]|_]-[].
+So = [[2, 1]|Si] .
+
+*/
\ No newline at end of file